ABSTRACT The anti-tick effect of Stylosanthes humilis and Stylosanthes hamata was evaluated for mature plants on plots experimentally infested with larvae of the cattle tick Boophilus microplus. Cenchurus ciliaris was used as control grass. The effect was evaluated counting the total number of live tick larvae recovered by the double flannel flag technique from the experimental plots during a four week period. The effect observed in both Stylosanthes species did not show significant differences (p > 0.05) between them and the larval survival percentage was 5.1 % for S. humilis and 7.5 % for S. hamata. In the first specie the anti-tick effect was lower than the one reported for young plants, but in S. hamata this effect was similar in young and mature plants. Further studies are necessary to complement the knowledge about this plant and to establish their use in field conditions..